In general, a hydraulic system is mounted in a construction machine to operate various operating devices. The hydraulic system receives power from an engine and operates a hydraulic pump, and operates various operating devices by working oil discharged from the hydraulic pump.
An electronically controllable electronic hydraulic pump is known as the hydraulic pump. Further, the hydraulic pump may be divided into a pressure control type.
The pressure control type electronic hydraulic pump may electronically control an angle of a swash plate to control a size of finally output pump torque. Further, the pressure control type electronic hydraulic pump is a type of controlling pressure of the pump in proportion to a detected pressure value of working oil.
As the related art, Patent Literature 1 “Apparatus and Method of Controlling Hydraulic Pump for Construction Machine” filed by the applicant of the present disclosure and published is known.
Patent Literature 1 relates to a method of controlling output torque of a hydraulic pump, and is a technology of mapping torque response performance of an engine to a time constant corresponding to a pump torque control means based on engine speed.
In order to find a time constant used for control in Patent Literature 1, it is very important to recognize a dynamic characteristic according to an engine speed, and the hydraulic system in the related art sets a time constant based on a reach of a load pattern from a standby load (zero or a predetermined level) to a full load to perform a control.
In the time constant control method, when a load is not the largest load, an inclination of output torque of a hydraulic pump is decreased, so that an engine speed is not decreased, but an operation speed is unintentionally decreased, thereby degrading workability.
Literature of related art: Korean Patent Application Laid-Open No. 10-2011-0073082 (Jun. 29, 2011)
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.